Water which contains undesired metals can exist as a result of many natural and man-made processes. For instance, mines (active and abandoned), chemical and metal finishing plants, photography and electronic device process plants and municipal water non-point source pollution are all sources of metal-containing water.
Prior to the present invention, the undesired metals were removed using either clarifier systems, ion exchange resins, polymeric membranes or electric semi-permeable membranes. The effectiveness of the clarifier system for removal of metals was highly variable and costly. The ion exchange resins or polymeric membrane systems were less variable but usually were more costly. This cost usually increased with time due to resin and/or membrane replacement.
In all systems except ion exchange, metals have been removed from water by essentially two conceptual steps:
a. chemical treatment (pH adjustment) followed by a
b. mechanical separation (filter or sedimentation)
In the present system, the two conceptual steps are also followed, with the improvement being decreased 10-year cost and high 10-year metal removal efficiency average. The system uses a chemical treatment stage (pH adjustment) and a mechanical separation (filter). The filter used, however, is one which was not originally designed for use in metal separation.
Previous to the present invention, inorganic cross-flow filters were used to separate organic solids from liquids in such areas a food processing juice clarification, fermentation filtration, etc.) and concentration of solids in uranium processing. In none of the previous uses of filtration were the particular uses or parameters for use described as they are in the present application.
It is therefore an object of the present invention to provide a method to remove metals from water in a cost effective and efficient manner using an inorganic cross-flow filter.
It is a further object to provide a method to purify metal-containing water using improved methods.
Definitions
For the purposes of the present invention, the following words and phrases shall have the meanings as set forth below:
xe2x80x9cElemental membranexe2x80x9d shall mean a membrane for an inorganic filter comprising alumina or zirconia.